1. Field of the Invention
This invention relates to an endoscope wherein the observing optical system can be prevented from being fogged.
2. Related Art Statement
Recently, an endoscope has come to be extensively used to observe a body cavity or the like or treat the same with treating tools by inserting the elongate insertion part into the body cavity or the like.
However, the endoscope to be used within the body cavity or the like must be used in a physiological saline solution or must be sterilized with a chemical solution and is therefore made of such waterproof and airtight structure as is shown, for example, in the gazette of Japanese Utility Model Laid Open No. 194722/1984 or the specification of West German Patent Laid Open No. 2062178.
Now, the conventional endoscope is made waterproof and airtight only in the outside fitting part. Therefore, the slightest amount of a water vapor entering the interior of the endoscope from outside will reach the interior of the observing optical system and will condense and fog the inside surface of the objective or the like and the observation will not be possible. Particularly, in the high pressure steam sterilization considered to be the most effective sterilization, a high temperature high pressure water vapor is used and a slight amount of the water vapor is very likely to enter the endoscope body even if the outside fitting is made.
By the way, in the gazette of Japanese Utility Model Laid Open No. 186420/1985, there is disclosed an endoscope wherein a moistureproof member made of a highly hygroscopic material is provided inside the endoscope body of a liquidtight structure.
Such hygroscopic material as slaked lime and active carbon shown in the above mentioned related art example and as silicagel and calcium carbonate are granular or powdery and are difficult to mold in the form of the interior of the endoscope. The moistureproof member formed of such hygroscopic material is likely to be broken and, in case it is broken, the observation will be likely to be obstructed by its fragments.